A couple things to work on to help this would be:
1. Bi-lateral breathing (alternating your breathing on both sides) is one way to ensure that you are rolling equally to both sides and your pull is equally strong on both sides.
2. Make sure that your head does not move unless you are breathing, because where your head goes your body will follow. Do a Tarzan drill (head up freestyle) for a half length without moving your head side to side and then put your head down and swim for second half concentrating on head position.
If you are rotating correctly you should feel that you are reaching out in front and taking fewer strokes by utilizing your lat muscles and not just your arms.
One of the common mistakes I see triathletes making is rolling their entire body too much and getting off balance. You always want your legs to be balancing out your roll and not simply following the roll.
Try these drills and swim stronger!